This invention relates to cold cathode discharge lamps and their electrodes.
Conventional gas discharge lamps take one of two forms. They are either of the hot-cathode or cold-cathode kind. In the hot-cathode kind, the electrodes are heated so that electrons are emitted from the cathode by primary emission; in the cold-cathode kind, ion bombardment of the cathode causes the secondary emission of electrons. Although hot-cathode lamps have a greater electrical efficiency, cold-cathode lamps have the advantage of a considerably longer life and maintain a more constant brightness over their life than hot-cathode lamps.
The electrodes of cold-cathode lamps are generally hollow, that is, they take the shape of a short tube having an open end and a closed end, the open end facing the opposite electrode. Electrodes of this shape have been found to produce a more stable discharge and require lower operating voltages than flat plate electrodes.